docs: def Fill(self, P=[(100, 0), (85, 15), (0, 3)], Color='blue', Alpha=0.3):
  
          '''
          Fill a region in planimetric rectangular coord.
          :param P: the peak points of the region in planimetric rectangular coord
          :type P: a list consist of at least three tuples, which are the points in planimetric rectangular coord
          :param Color: the color used to fill the region
          :type Color: a string; b: blue, g: green, r: red, c: cyan, m: magenta, y: yellow, k: black, w: white
          :param Alpha: the transparency used to fill the region
          :type Alpha: a float number from 0 to 1, higher darker, lower more transparent
          '''
          a = []
          b = []
  
          for i in P:
              a.append(i[0])
              b.append(i[1])
  
          return (a, b)